Got another one…
It appears that if the serve restarts crafting stations that don’t normally have more than 1 thrall slot, will reset to having only 1 thrall slot.
Example:
I have a Scoutwright and a Shieldwright. I had to demolish and rebuild both of my armor benches (Improved and Campaign) in order to get the two Thralls to show up.
The server has since gone through several restarts and, now that I’m making another armor set, I see only my Shieldwright is “slotted”. BUT if I build another randomly-placed Improved bench bot show up in that one.
So…found another instance of the state of something being reset to ‘default’ upon server restart (the other being golems).